In order to accommodate increased recording density of magnetic recording media, the surface property of the constituent magnetic layers has been smoothened. For this reason, the coefficient of friction of the magnetic layers with the respective parts of a recording and reproducing apparatus is disadvantageously increased, to thereby hinder smooth running of the magnetic recording media and toresult in damage to the magnetic layers.
Furthermore, since the use of video tape recorders (VTR), personal computers, word processors, etc. has recently become popular, magnetic recording media are used under wider conditions of temperature and humidity. It has therefore been desired to provide magnetic recording media of both high quality and durability.
In order to address such problems, the use of various lubricating agents has been proposed.
The use of straight chain fatty acids as lubricating agents has been proposed in JP-B-51-39081 (the term "JP-B" as used herein means an "examined Japanese patent publication"). Straight chain fatty acids such as stearic acid have a strong effect of lowering the .mu.value (coefficient of friction), but tend to generate white powder due to their high melting point which causes head clogging or an increase in drop out (hereinafter referred to as "DO"). In order to prevent the generation of white powder, the use of various branched chain fatty acids having a low melting point has been proposed.
For example, JP-B-48-15077 discloses magnetic layers containing branched chain fatty acids having a melting point of 20.degree. C. or less and at least 12 carbon atoms. All of the fatty acids are branched chain fatty acids having different branched carbon chain lengths. JP-A-59-172131 and JP-A-59-172133 disclose magnetic layers containing naphthenic acids. These are cyclic fatty acids (the term "JP-A" as used herein means an "unexamined published Japanese patent application").
The branched chain fatty acids having different carbon chain lengths and the cyclic fatty acids have a low melting point, but do not have the effect of lowering the .mu. value. As a result, these fatty acids do not sufficiently improve running tension.
Furthermore, JP-A-2-56722 discloses branched chain fatty acid esters. Although the still durability can be significantly improved by using such esters, the number of DOs (dropouts) and the head clogging are not improved when the esters comprise conventional fatty acids. As long as conventional fatty acids are used, it has been desired to concurrently solve the problems of dropout, head clogging and running tension.